The present invention relates to infant supports that provide both incubator and warmer configurations, and, more particularly, to temperature control systems for such infant supports during transition between incubator and warmer configurations.
Newborns and premature infants often require isolation in a controlled environment for proper development. Incubators provide such an environment by providing a canopy forming an enclosure surrounding an infant support surface. The environment within the enclosure is controlled so that the oxygen content, air temperature, noise levels and other environmental parameters are maintained at levels conducive to infant development. The air temperature within the enclosure is an environmental factors which highly influences an infant""s core temperature as indicated by its skin temperature. Incubators include temperature sensors to provide an indication of the air temperature within the enclosure and an indication of the skin temperature of the infant. The air temperature within the enclosure is adjusted by infusion of warmed air into the enclosure. Warm air infusion is accomplished by a system including a blower or fan for drawing external and/or internal air past a heater for introduction into the enclosure through orifices.
Often newborns and infants also require various procedures to be performed on them by one or more caregivers. While the canopy and walls of an incubator includes access panels and orifices permitting access to an infant within the enclosure, this access is often too limited to perform all of the necessary procedures. Warmers provide relatively unobstructed access to an infant or newborn. Typically when relatively unobstructed access to an infant in a dedicated incubator is required, the infant is moved from the dedicated incubator to a dedicated warmer. The movement disturbs the infant and often requires the removal of sensors and tubes which further disturbs the infant. The move from the incubator to the warner typically does not adversely affect the core temperature of the infant. After the procedures are performed on the infant, the infant is typically returned to an incubator. Insertion of the infant into the incubator requires reconfiguration of the access panels in the walls canopy permitting warmed air to escape from the enclosure. Often the time required for the incubator to stabilize the skin temperature of the infant is unduly long.
Infant supports having the capability to serve as both incubators and warmers are known and were developed to address sone of the issues arising from the use of dedicated incubators and dedicated warmers. Such infant supports are shown and described in Donnelly et al., U.S. Pat. No. 5,453,077, issued Sep. 26, 1995; Donnelly et al., U.S. Pat. No. 5,817,002, issued Oct. 6, 1998; Moll et al., U.S. Pat. No. 5,817,003, issued Oct. 6, 1998; Goldberg et al., U.S. Pat. No. 5,759,149, issued Jun. 2, 1998; Newkirk et al., U.S. Pat. No. 5,971,913, issued Oct. 26, 1999; Donnelly et al., U.S. Pat. No. 5,971,914, issued Oct. 26, 1999; Goldberg et al., U.S. Pat. No. 6,022,310, issued Feb. 8, 2000, Goldberg et al., U.S. Pat. No. 6,024,694, issued Feb. 15, 2000; Goldberg et al., U.S. Pat. No. 6,036,634, issued Mar. 14, 2000, Prows et al., U.S. Pat. No. 6,049,924, issued Apr. 18, 2000; Speraw et al., U.S. Pat. No. 6,071,228, issued Jun. 6, 2000; Donnelly et al., U.S. Pat. No. 6,270,452, issued Aug. 7, 2001; Goldberg et al., U.S. Pat. No. 6,296,606, issued Oct. 2, 2001; and Prows et al., U.S. Pat. No. 6,345,402, issued Feb. 12, 2002, the complete disclosures of which are hereby expressly incorporated by reference. Such infant supports are also shown and described in U.S. patent application Ser. No. 09/688,528 filed on Oct. 16, 2000 and U.S. patent application Ser. No. 09/571,449, filed on May 16, 2000, assigned to the common assignee of the present application, the complete disclosures of which are hereby expressly incorporated by reference.
Such incubator/warmers include an infant support surface resting on a housing that incorporates systems similar to standard incubators facilitating control of the environment surrounding the infant when the canopy and walls are configured in a closed state and the incubator/warmer is acting in incubator mode. The incubator/warmer 110 also includes a radiant heater which directly warms the skin of the infant when some or all of the canopy and walls are configured to an open state and the incubator/warmer is in a warmer configuration. Such incubator/warmers are adapted to facilitate a transition from incubator to warmer configuration and from warmer to incubator configuration. During transition from incubator to warmer configuration, the walls and the canopy are configured to provide relatively unobstructed access to the infant and an infrared radiant heater is activated to directly warm the skin of the infant. When the walls and the canopy are configured to provide such free access, the warm air adjacent the infant dissipates throughout the room in which the incubator/warmer is located. Thus, the air adjacent the infant quickly approaches the ambient air temperature of the room allowing convective heat loss from the infant""s skin to the surrounding air. The infrared heater, by directly warming the infant""s skin is able to compensate quickly for the convective heat loss from the infant to maintain the core temperature of the infant at desired levels.
When the incubator/warmer is transited from the warmer configuration to the incubator configuration, the walls and canopy are configured to a closed state forming an enclosure around the infant support surface. During transition to the closed state air at or near ambient room temperature may be trapped within the enclosure. Certain infrared radiant heaters are not very effective in maintaining the infant""s skin temperature when the walls and the canopy are closed because the canopy and walls may be opaque to infrared radiation or the refractive index of the optically transparent walls and canopy may cause reflection of much of the incident infrared radiation. Thus, after transition from warmer configuration to incubator configuration, time is required to raise the temperature of the air within the enclosure from near ambient room temperature to a temperature sufficient to maintain the skin and core temperature of the infant. It has been found that fluctuations in the core temperature of an infant can adversely affect their development.
The infant support thermal control system disclosed herein controls a convective heater and blower of an infant support during a priming stage when the support is acting as a warmer to reduce the time required for the support to stabilize the temperature of the infant at desired levels after transition to incubator configuration. The control system may also control the radiant heater of an incubator/warmer in warmer configuration and the convective heater and blower of the incubator/warmer after transition between warmer configuration and incubator configuration. The controller operates the blower and convective heater during the priming stage to reduce the time required for the incubator/warmer to stabilize the temperature of the infant at desired levels. The controller may also control infrared heater operation in the warmer configuration to compensate for infant heating attributable to the operation of the blower and convective heater during the primer stage.
Typically, during the incubator configuration, an infant is isolated from the outside environment by side and end walls cooperating with a canopy that surrounds an infant support surface forming an enclosure. A convective heater and blower are provided in the support to direct warm air into the enclosure for controlling the temperature of the air therein. Such a system typically comprises a blower, a heater and passageways. The passageways communicate between the heater and blower to direct warm air produced by the heater and blower into the enclosure. During the warmer mode, the canopy is raised and the enclosure is opened. A radiant heater is also typically included with the support to direct radiant heat to the infant while exposed to the outside environment.
Temperature sensors are also provided with the infant support to monitor and control the temperature and relative humidity of the air adjacent the infant. Such sensors are shown and described in U.S. Provisional Patent Application Nos. 60/199,103, entitled Fail Safe Device for Incubator and Warmer, filed on Apr. 21, 2000, and 60/258,011, entitled Humidity Sensor for Incubator, filed on Dec. 22, 2000, the complete disclosures of which are hereby expressly incorporated by reference. Illustratively, the fail-safe device includes a temperature sensor assembly wherein one sensor is associated with a heating element that generates the heat, and a second sensor is associated with at least one of a plurality of air-contacting fins that distributes the heat. The second sensor is a back-up that provides an independent measurement of the temperature that can be correlated with the temperature measurement of the first sensor. A control system is also provided that monitors the sensors to prevent the infant support from becoming too warm.
The illustrative humidity sensor is an assembly that comprises a first sensor spaced apart from the infant positioned on the support surface. The temperature of the air drawn from the enclosure is measured. In addition, the temperature of the air adjacent a humidity sensor is measured by a second sensor.
In conventional incubator/warmers, during transition of the infant support from the incubator to warmer configuration, the infrared heater elements typically respond quickly enough to maintain the infant""s core temperature within a reasonable variation. When transiting the infant support from the warmer to incubator configuration, however, the response of the convective heater may be inadequate to maintain the infant""s core temperature within the reasonable variation.
Conventionally, during the incubator mode, the temperature of the air adjacent the infant maintains the temperature of the infant. During warmer mode, however, the convective heater is often not used. Rather, the radiant heater warms the infant directly. The radiant heater, however, does not warm the surrounding air. Because the incubator/warmer, when in the warmer configuration, does not isolate the infant from the outside environment, a temperature change occurs in the air adjacent the infant. Consequently, during the return transition from warmer to incubator configuration, the initial temperature of the air inside the enclosure is closer to that of the outside environment, which is most often lower than the desired air temperature for the incubator mode. Substantial time may be required for the convective heating system to warm the enclosure to the desired temperature.
Accordingly, the thermal control system of the present disclosure reduces the time it takes for the enclosure to reach the desired temperature after the support transitions from the warmer to the incubator configuration. During the warmer mode, the infant support illustratively uses a variable priming mechanism to regulate a thermal infusion of a known magnitude at transition. This will allow for a rapid response to the transition, since the convective heater will already be warmed. In addition, heating the surfaces and volumes within the air passages creates a heat reservoir, which may be infused into the enclosure after transition from warmer configuration to incubator configuration to quickly increase the air temperature needed to sustain the core temperature of the infant. Upon transition into incubator configuration, the infant support will adapt the convective PID error for convergence to the targeted temperature set point.
An incubator/warmer, in accordance with one aspect of the disclosure, includes an infant support, a canopy, a convective heating system, a radiant warmer and a control system. The canopy provides an enclosure about the infant support and an infant residing on the support when the incubator/warmer is in an incubator configuration. The canopy is retractable to place incubator/warmer in a warmer configuration. The convective heater system includes an air heater, a blower and passageways through which air is circulated by the blower to provide heated air to the enclosure. The radiant warmer is positioned to warm the infant on the support when the canopy is retracted and the incubator/warmer is in the warmer configuration. The control system is configured to rapidly bring air in the enclosure to a target temperature when the incubator/warmer transitions from the warmer configuration to the heater configuration. The control system includes a priming stage algorithm that maintains air in the passageways of the convective heater system at a priming temperature by controlling power to the air heater while the incubator/warmer is in the warmer configuration and an infusion stage algorithm that controls the blower to drive air from the passageways into the enclosure to rapidly warm the enclosure after transition of the incubator/warmer to the incubator configuration. The incubator/warmer may also include a convergence stage algorithm that controls the blower to drive warmed air into the enclosure until the target temperature is reached.
According to another aspect of the disclosure, a control system for an infant support of the type capable of assuming and transiting between an incubator configuration wherein an enclosure is defined around an infant support surface and a warmer configuration is disclosed. The infant support has a radiant heater supplied with power in the warmer configuration, a convective heater, a blower and duct work communicating with the enclosure, convective heater and blower. The control system includes a convective heater controller and a blower controller. The convective heater controller controls the power to the convective heater prior to the infant support assuming the incubator configuration so as to prewarm portions of the duct work past which air to be infused into the enclosure will pass. The blower controller controls the power to a blower to provide a slight air flow prior to the infant support assuming the incubator configuration and to provide an increased air flow upon the infant support assuming the incubator configuration.
According to another aspect of the disclosure, a control system for an infant support of the type capable of assuming and transiting between a closed configuration wherein an enclosure is defined around an infant support surface and an open configuration is provided. The infant support has a convective heater, a blower and duct work communicating with the enclosure, convective heater and blower. The control system includes a convective heater controller and a blower controller. The convective heater controller controls the power to the convective heater prior to the infant support duct work assuming the closed configuration so as to prewarm portions of the duct work past which air to be infused into the enclosure will pass. The blower controller controls the power to the blower to provide a slight air flow prior to the infant support assuming the closed configuration.
According to yet another aspect of the disclosure a method of controlling the temperature of an infant in an incubator/warmer is provided. The incubator/warmer is of the type having an open configuration for operating as an infant warmer, a closed configuration forming an enclosure for operating as an incubator. The incubator/warmer includes a housing supporting an infant support, an air temperature sensor positioned to be within the enclosure when the incubator/warmer is in the closed configuration, a radiant heater, and an air heating system including an air heater, a blower and duct work located in the housing below the infant support. The duct work is in fluid communication with the enclosure. The method comprises the steps of operating the air heater while the incubator/warmer is in the open configuration to generate a heat reservoir and infusing the heat from the generated heat reservoir into the enclosure upon incubator/warmer attaining the closed configuration.
Additional features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.